Three survivors said most of those who drowned were Pakistani nationals.

The UN agency says Pakistani nationals had been taking an increasingly large share of migrants trying to cross the Mediterranean via Libya to Europe.

Libya is the main gateway for migrants trying to cross to Europe by sea, though numbers have dropped sharply since July as Libyan factions and authorities – under pressure from Italy and the European Union – have begun to block departures.

More than 600,000 people are believed to have made the journey from Libya to Italy over the past four years.